We investigated factors affecting net transperitoneal calcium balance (Ca-BL) and the level of parathyroid hormone in relation to stepwise changes in serum calcium, by short PET (peritoneal equibrium test during 240 min: using 2000 ml of 2. 5% dextrose dialysate containing 1. 75 mmol/L Ca) in uremic patients undergoing stable CAPD. We calculated Ca-BL (mg/effluent/PET) of 244 effluents obtained from 90 patients receiving calcium carbonate as a phosphate binder without vitamin D supplementation. Their serum calcium level corrected with albumin (cSCa), alkaline phosphatase activity (ALP) and intact-PTH level was 9. 7 + 0. 9 mg/dl, 236±83 mlU/ml and 153. 0±172. 4 pg/ml, respectively. We proposed two statistic significant regression lines between Ca-BL and total drainage effluent volume (Ca-BL = 133X-0. 056: r = 0. 981, P<0. 001), cSCa (Ca-BL= –12. 9X + 123. 6: r = 0. 941, P<0. 01). Total drainage volume (TDV) and cSCa were two major factors affecting Ca-BL. A TDV level of 2430 ml/240 min-PET or more was required for positive Ca-BL in cases with 9. 5-10. 0 mg/dl of cSCa, using this linear regression analysis. A cSCa level of 9. 6 mg/dl or more was also required for positive Ca-BL in cases with 2400-2600 ml/240min-PET. We also proposed a significant linear regression line between the intact-PTH level and cSCa (i-PTH= -90. 5X + 1015. 8, r = 0. 973, P<0. 01). This line suggest that 200 pg/ml of intact PTH was obtained by 9. 0 mg/dl or less of cSCa level in 90 CAPD uremic patients. However, this cSCa level was difficult to obtain through CAPD therapy with the dialysate used (Ca = l. 75 mmol/L) for positive net transperitoneal Ca-BL. In conclusion, the 1. 75 mmol/L calcium dialysate may have induced relative secondary hypoparathyroidism with low turnover bone in CAPD uremic patients receiving calcium medication as a phosphate binder. We recommend the replacement therapy with less concentrated calcium dialysate for CAPD patients without a high parathyroid hormone level.
- continuous ambulatory peritoneal dialysis (CAPD)
- low calcium dialysate
- low turnover bone
- transperitoneal calcium balance (Ca-BL)
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